Telepidlqne-translvlitter



. 42 Sheets-sheeti. J. HQIRWIN. l

` Telephone-Tra,nsmitter.

No. 225,388. 'Patented Mar'. 9,1880;

l nu

@@m@ @QQ IL PEIERS. FMWD:EX'I'MQGRAPMEN.4 WASHINGTON. Dv U.

UNITED vSTATES PATENT OFFICE..

JOHN H. IRWIN, OF MORTON, PENNSYLVANIA.

TELERnoNE-TRANSMITTE R.

y SPECIFICATION fermihg` part ef Letters Patent No. 225,3@ dated Meren9, 1880.

Application inea Deeember 19, 1879;

To allwhom t may concern Be it known that I, JOHN `H. IRWIN, of Morton,in thecounty of Delaware, in the State of Pennsylvania, have invented,new and useful Improvements in Acoustic Telegraphs; and I do herebydeclare that the following is a full and exact description of the same.

In all telephones the medium of transmis-` sion is necessarily onecapable of responding4 to the vibrations of sound-waves, and in allelectric telephones the responsive vibration of such medium istransformed intonndulations of the electrical current by means of aplane of variable resistancein the line wherein the resistance is madevariable by the vibrations referred to. The sensitive medium'referred tohas generally been in the form of a disk of some elastic material.

The adjustments of the points of contact and 'resistance to producethe"` desired effect areexceedingly delicate; and it is a desideratum toobtain suoli an adjustment and such qualities of vibration aswill enablethe instrument torespond to vocal' articulations uttered in a low toneclose to the' sensitive medium without being capable of responding toall of those sounds which are ordinarily so delicate as to be inaudibletothe unaidedear. The reason for this `is manifest, because an'instrument may be capable of transmitting all of thearticulate sounds ofwords spoken in its vicinity, and also'capable of transmitting` a greatmultitude of soundswhich are practically inaudible in themselves, butare' made I audible tothe listener at the receiving-instrument, and withthe effect there of confusingithe words spokenat thetransmitting-instrument, so that it isdifflcult for the listener toseparate the articulate sounds from the inarticulat'e ones.

i I have secured the desired result in a very satisfactorymanner bydamperin g the sensitive medium of the transmitting-instrumentwith somesuitable elastic fibrous material distributed over the surface of thediaphragm. I will' herein describe such an" arrangement and suchmaterial as I have found" to besatis-` factory.

In my' patent dated October 22,1878,No. 5o

209,266, I have described a needle, preferably pointed with platinum, incontact with another needle or pencil, preferably of carbon, supportedby means of a spring, and specitied in said patent that said elasticsupport might be either above or below said needle, the essential matterbeing the maintenance of said contact ,witha pressure of the requisitedelicacy and as nearly uniform as possible.`

In the instrument shown and described in said patent thesensitive mediumabove mentioned was the base of the instrument itself. In this patentthe sensitive medium described is a thin disk of metal, mica, or othersuitable material secured to the base of the instrument, and a needle,preferably ,of platinum, with its end resting upon the center of saiddisk. I prefer to interpose between said disk andthe end of said needlea body of carbon, which, for this purpose, maybe a` thin slice of smalldiameter, which it is convenient to secure to the disk by means ofsolder, the under surface of thecarbon having been previouslyelectroplated with copper for the purpose of euabling the solder toadhere; and my present improvement relates to the damperin g of saiddisk to reduce its power of response to sounds more delicate than thelow tones of the voice, so that said vocal tone'A or tones of similarvolume aloneshall be transmitted.

That othersmay fully understand my invention, I will more particularlydescribe the method lof carrying it into effect which I prefer, without,however, limiting myself exactly to the details of structure or tothematerials described, and having reference to the accompanying drawings,wherein- Figure l is a vertical section of the instrument in the formwhich I prefer to give it. Fig. 2 is a diagram exhibiting the method ofuse which I have preferred. Fig. 3 represents, in sectional perspective,my instrument arranged as a stationary transmitter. Fig. 4 is alongitudinal vertical section of the same; Fig. 5 represents amodification in structure.

A is the supporting frame-work of the instrument. It may be'of any formdesired or` suitable. In said frame-work there are propby me.

erly arranged anti-friction guides b b for the needle C, as heretoforedescribed and patented One end of said needle is mounted \upon a spring,D, which I prefer to make of iine coiled wire.v Said spring is attachedat one end to said needle and at the other end to an adjusting-rod, E,which is capable of longitudinal motion in a bearing, F," for thepurpose of adjusting the pressure of the spring 1o D. The spring D maybe made of a fiat elastic strip, or in other forms, if desired; but Iprefer a spring of coiled wire, as shown.

The free end of the needle G rests upon the center jof the elastic diskG, the edges of which are supported by the frame A. The disk G is asensitive medium, which is caused to vibrate by the impact ofsound-waves. The point of contact between said disk and the needleconstitutes the point of varying resistance in the electric line,wherein the resistanceis varied by the vibrations of the disk G inresponse to the impact of sound-Waves. I prefer to interpose betweensaid disk and the end of the needle C a thin slice of carbon, G, whichmay be electroplated and soldered to said disk, as hereinbefore setforth.

The instrument constructed as described is capable of transmittingsounds so delicate that they are inaudible to the nnaided ear, and thepurpose of my invention is to modify this capacity so that said diskwill be less sensitive, and only transmit the articulate tones of thevoice, and for this purpose I place in con tact with said disk aquantity of elastic fibrous material, H, and I have found loose wool,silk, or cotton to be highly satisfactory. To confine this elasticmaterial in contact with said disk, I place a second disk, I, in theframework A, parallel with the disk G, and place said elastic materialbetween said disks, and submit said elastic material to such a degree ofcompression as may be found most advantageous by pressing the disk Itoward the disk G. This degree of compression, however, is very slight'.

Disks G and I are not rigidly confined at their edges, and are thereforecapable of motion bodily to or from each other, so that under the impactof sound-waves the said disk may move without buckling at some pointbetween the center and edge, and therefore short nodal points aredesignated in the `vibration of these disks, and disks of larger sizethan usual may, for that reason, be em ployed.

rlhe force imparted to the spring D is such that the needle C will bemaintained in contact with the disk G with that certain force wherebythe best results are maintained. That certain force must beexperimentally deter mined by each instrument, and the pressure of thespring D is so adjusted that the needle is maintained with anapproximate uniform force in contact with said disk, in whateverpofixesthe rod E at any point of adjustment desired.

Fig. 3 represents a modified form of damp ered instrument, which, forsome purpose or some situations, may be preferred to theneedle-instrument above described. In this modified instrument theinclosing-case is a cylinder having a mouth-piece at one end and anadjusting-screw and piston at the opposite end. Near about the centerthere are two transverse disks or diaphragms, unattached to thecylinder, and each provided at its center and opposite to each otherwith two small disks of carbon. rIhe electric line-wires enter saidcylinder through properly insulated oriiices, and are connectedseverally with said disks. Now, the space within said cylinder andbetween said disks is occupied by some elastic ibrous substance,preferably wool, silk, or cotton, as hereinbefore set forth, and thesame is put under the requisite compression by means of theadjusting-screw first mentioned.

In diagram 2 I have represented the manner of mounting and connectingthe electric circuit with these instruments which I have found to besatisfactory and advantageous.

L L are the batteries, one at each station. M M are induction-coils, theprimary wires of 1o which are connected at one side with the battery L,and at the other side with the instrument A by the wires m n, so as tocom# stitute a closed circuit with the battery.-

Ihe secondary or induction coil is connected at one endwith the earth bythe wire I?, and at the other end constitutes a line-wire, Q, whichextends to the next and succeeding station, which is similarly providedwith battery, transmitter, and induction-coil. Ordinarily, with eachtransmitting-instrument A there is also a receiving-instrument, It,which may be of any improved style, and said. instrument is placed inthe line Q. If, vhowever, for any reason said receiving-instrument isabsent, the transmitting-instrument A may be used as a receiver. Theline Q will then extend from one induction-coil M to the similarinduction-coil at the next station. I

Having described my invention, what `I claim as new is- 1. In atelephone, a sensitive freely-vibrat ing medium which is not lundertension, com- IIO IIS

bined with a damper composed of a suitably- 3. In a te1ephone,asensitive vibrating disk, elastic fibrous material, substantially as setQ, having free edges and capable of vibrat- 1o forth. ing bodily,combined with electrodes main- 2. In a telephone having a sensitive orvitained in Contact. i 5 brating disk, G, a damper, H, composed of J. H.IRWIN.

some suitably-elastic material, and a second Witnesses: disk, I, wherebysaid damper material is com- R. D. O. SMITH,

pressed and held in contact with the disk G. N. B. SMITH.

